VBRCpy: Very Broadband Rheology Calculator (Python)

About this technology

Overview

Geodynamic models often require 3D mantle structure as input, and seismic tomography provides seismic shear wave (Vs) and quality factor (Q) observations throughout the mantle that can constrain this structure. Interpreting these Vs and Q anomalies in terms of temperature and viscosity variations requires understanding both anharmonic and anelastic behavior of mantle minerals. VBRCpy is an open-source package that derives temperature and viscosity structure from seismic tomography models via Bayesian inversion of shear-wave velocity (Vs) and/or quality factor (Q). This software builds upon the Very Broadband Rheology Calculator (Havlin et al., 2021), reimplemented as a standalone Python package with expanded capabilities. Using one of four available laboratory-calibrated anelastic methods (extended Burgers, Andrade, Maxwell frequency scaling, and homologous temperature scaling), observed Vs and/or Q are evaluated against precomputed parameter sweeps via Bayesian inference to recover full posterior probability distributions of temperature, melt fraction, and grain size, from which viscosity is computed. Enhancements include: (1) direct viscosity output with uncertainty propagation; (2) depth-dependent density from a chosen Earth model; (3) implementation of additional elastic parameter compilations, extending applicability towards transition zone depths; (4) support for multiple input data formats (NetCDF, CSV, MAT); (5) parallelization for efficient inversion of large tomography models; and (6) YAML/JSON configuration with a clean command-line interface. This package is benchmarked against the outputs of the original codebase and can provide 3D viscosity and temperature estimates with quantified uncertainties suitable for glacial isostatic adjustment modeling.